Why Is My “Check Engine” Light On?

Have you ever looked at your dashboard and asked yourself why is my check engine light on?

Why Is My “Check Engine” Light On?

  1. Broken or Loose Gas Tank Cap
  2. Having a Faulty O2 Sensor
  3. Faulty Air Intake System
  4. Faulty MAF Sensor
  5. Dirty or Clogged Catalytic Converter
  6. Bad Car Battery
  7. Faulty Spark Plugs
  8. Electronic Fault
Why Is My Check Engine Light On

A ”check engine” light is something that all of us have seen. It doesn’t have to mean that something is wrong with your engine. The check engine light usually covers up to 10 errors. Not sure why, but it’s the way that manufacturers created all the cars. Are you asking yourself what could cause a check engine light to come on? I have created a list of the 8 most common errors that will turn on the check engine light on your vehicle

1. Broken or Loose Gas Tank Cap

Problem: The first place you should look at if you get the check engine lights on is the gas tank cap. There are two most common reasons why this causes problems.

  1. Your check engine light could be on if your gas tank cap is loose. This happens a lot. You probably didn’t tighten it when you poured gas.
  2. The the gas tank cap seal inside is worn out and causes the check engine light to turn on.

The problem with the tank cap being loose or the seal being worn out is that if the gas tank isn’t closed properly, air gets into the gas tank and causes a problem in the fuel mixture.

Solution: If this is the issue, you are lucky because this is the cheapest fix. Don’t bother fixing the cap sealant. You can get a new gas tank cap on amazon.com.

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2. Having a Faulty O2 Sensor

Problem: A common reason for the check engine light to go on is the O2 sensor. On most cars, the O2 sensor is located on the exhaust system. It can be on the beginning of the exhaust manifold or lower on the exhaust system on a pipe. The problem is that if the O2 sensor is faulty it will give a bad reading exhaust fumes thus causing the check engine lights to go on.

Solution: If you have an OBD scanner(get OBD on amazon.com), you can run diagnostics on your car and see if it has some exhaust error codes. The solution to the O2 sensor problem is of course replacing it.

3. Bad Air Intake System

Problem: Another problem that makes the check engine light to go on is a faulty air intake system. You should check the whole of the air intake system for loose hoses, punctures and bad seals. This is one of the most common reasons for the check engine light to go on. If you have a loose air hose or a puncture on one of the air hoses, your check engine light will definitely turn on. You can perform this check, or you can take your car to the mechanic.

Solution: If you find any loose hoses, you can tight them with a screw. If you have punctured hoses or bad seals, you need to replace those hoses.

4. The MAF Sensor Is Faulty

Problem: Another thing you should check is the MAF sensor. The MAF stands for Mass Air Flow sensor. That sensor is located on the air intake of the car and its purpose is to regulate the amount of air that goes into the air intake.

Solution: When you get this problem, the best repair is to either replace it altogether or take it off and clean it. The best way to see if you have a faulty MAF sensor is with your OBD scanner.

See Our Other Content: How To Clean Your Fuel Tank Without Removing It

5. Dirty Or Clogged Catalytic Converter

Problem: A dirty or clogged catalytic converter can make your check engine light turn on. The catalytic converter is located under the car, on the exhaust system. Because of its location, over time it gets dirty and clogged, causing the o2 sensor to give a bad reading on the exhaust fumes.

Solution: The solution to this is either changing the whole catalytic converter or to take it off and clean it. To be honest, cleaning it will solve your issue for the moment, but its best if you just change it.

6. Bad Car Battery

Why Is My Check Engine Light On

Problem: Having an old and worn car battery is also a common reason why the check engine light goes on. If your car battery is giving out improper voltage, the car computer will record it and will turn on your check engine light.

Solution: The solution Check the alternator voltage output. If the alternator voltage output is too high or too low, it can cause the check engine light to go on. The car battery reading should be 12.6 volts. To make this check all you need it is a multi meter (get one on amazon.com).

7. Faulty Spark Plugs

Problem: Faulty spark plugs or spark plug cables is a rare reason for the check engine light to go on, but nevertheless, give it a check. If you change the spark plugs on a regular service interval, you shouldn’t have any problems with that. The spark plug cables are are built to last a very long time, so they shouldn’t cause problems.

Solution: If you have faulty spark plugs or worn spark plug cables, it’s best if you replace them.

8. Electronic Fault

Problem: The final reason the check engine light can go on is a electronic or electric fault on your car. So, things like short circuits, or a broken cable somewhere, or a faulty ECU unit can cause the check engine light to go on. Newer have a separate warning light in case you get an electric or electronic fault, but the older models have that good ol’ engine light.

Solution: The solution to this is an OBD code reader. You have to find what the fault is. This is perhaps the most tricky one, but with the OBD scanner, you can do it easily.

How urgent is the check engine light?

A check engine light is something that we all hate to see, but how urgent is it? Do we have to stop driving the car immediately? Should we call a tow truck? This issue is an urgent thing. If you see your check engine light go on, you need to take your car to the mechanic immediately. It could be a false flag, but if you disregard it, in the long term it can cause serious damage to your car.

Is your engine oil due for a change? Visit our Car Fluid Guide Website to learn the importance of changing your oil on time, which type of engine oil is best for your vehicle, and much more.

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Hi there. I am a certified Automotive Service Excellence (ASE) mechanic since 2018 and a car detailer for 10 years.

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